The present invention relates to a horizontal-contour emphasizing signal processor to be incorporated in video-signal processor of conventional or high-definition television receiver.
A structure of horizontal-contour emphasizing signal processor incorporated within conventional television receiver is now explained next. FIG. 1 shows a block diagram of said processor circuit, and FIGS. 2(a)-2(g) show signal-waveforms observed at various points in said block diagram shown in FIG. 1.
In FIG. 1, 1 is a first delay-circuit, 2 is a second delay-circuit, 3 is a synthesizing circuit, 4 is a first subtraction circuit, 5 is a second subtraction circuit, and 6 is a third subtraction circuit. FIG. 2(a) illustrates an input luminance-signal, FIG. 2(b) illustrates an output signal of first delay-circuit 1, FIG. 2(c) illustrates an output-signal of second delay-circuit 2, FIG. 2(d) illustrates an output-signal of first subtraction circuit 4, FIG. 2(e) illustrates an output-signal of second subtraction circuit 5, FIG. 2(f) illustrates an output-signal of third subtraction circuit 6, and FIG. 2(g) illustrates an output luminance-signal. The output-signal illustrated in FIG. 2(f) is a horizontal contour emphasizing signal.
The operation of thus constructed horizontal-contour emphasizing signal processor incorporated in conventional television receiver is now explained by referring FIGS. 1 and 2(a)-2(g). The input luminance-signal of FIG. 2(a) is supplied to first delay-circuit 1 and to first subtraction circuit 4 at the same time, and the output-signal of FIG. 2(b) is produced at the output of first delay-circuit 1.
Then output-signal of FIG. 2(b) is supplied to second delay-circuit 2, first subtraction circuit 4, second subtraction circuit 5, and synthesizing circuit 3, producing the output-signal of FIG. 2(c) at the output of second delay-circuit 2, and the output-signal of FIG. 2(d) at the output of first subtraction circuit 4.
The output signal of FIG. 2(c) of second delay-circuit 2 is supplied to second subtraction-circuit 5, producing the output-signal of FIG. 2(e) at the output of second subtraction-circuit 5. Then, the output-signal of FIG. 2(e) of second subtraction circuit is subtracted from the output-signal of FIG. 2(d) of first subtraction circuit 4 by using third subtraction circuit 6 producing the output-signal of FIG. 2(f) of the third subtraction circuit 6.
On the other hand, the output-signal of FIG. 2(f) is supplied to synthesizing circuit 3 as a horizontal contour emphasizing signal, and the output-signal of FIG. 2(b) of first delay-circuit 1 is synthesized properly with the horizontal contour emphasizing signal, and the output luminance-signal of FIG. 2(g) is produced by this.
As seen from the waveforms shown in FIGS. 2(a)-(g), when synthesizing circuit 3 of conventional construction is employed to synthesize the horizontal-contour emphasizing signal, spreads of its signal components over the period corresponding to the first delay time produced by said first delay-circuit 1 at first and the second delay-time produced later by second delay circuit 2 during the luminance signal change, are produced.
Therefore, a horizontal-contour emphasizing signal of poor quality is produced by this, and thus, this is unsatisfactory to produce the video-signals for high-definition television.